Internet Filtering in China in 2004 2005 

Figure 27   Blocked Sites With Accessible Top Level URLs 

www.stanford.edu/group/falun/ 

public.planetmirror.com/pub/abit/download/drivers_update/voanews.com/ 

www.stumbleupon.com/url/www.voanews.com/ 

www.let.leidenuniv.nl/bth/falun.htm 

This pattern may indicate filtering by URL string, blocking with no effort to investigate the nature 

of the content at a page, or an extremely aggressive attempt to locate and filter offensive content while 

preserving access to the bulk of the content of domains containing one or more site related to generally 

filtered content. 

F. E mail Filtering 

E mail is a vital Internet communications tool; ONI conducted a brief series of tests to evaluate 

whether, and how, China filters messages with sensitive content.  Our results suggest that China does not 

filter e mail messages at the backbone level of its network; instead, filtering is more likely to be performed 

by individual e mail service providers, with little consistency among providers.

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Filtering technology for e mail messages is well developed due to the need to combat unsolicited 

bulk e mail messages, commonly known as  spam.   Spam filters are typically installed on e mail servers; 

these filters search for specific patterns, keywords, or other characteristics of spam messages, such as 

altered message headers.  If the filter detects a message that matches its definition of spam, it will 

typically reject the e mail message, quarantine it, or tag it as spam.  Many ISPs also block access to the IP 

addresses of mail servers associated with spammers.  

To test China's e mail filtering, ONI acquired five e mail accounts (addresses) from free e mail 

service providers in China.  We created ten e mail messages with sensitive content in the subject line and 

body text.

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  We based the content of these messages on the monthly news summaries of significant 

events in China compiled by Human Rights In China (HRIC); these include information on arrests of 

political dissidents and religious persecution.  We sent each of these ten messages in English to all five e 

mail accounts in China from two different e mail accounts hosted outside China. We also sent each of the 

messages in Chinese twice (once encoded in the GB 2312 character set and once in Unicode) to the five e 

mail accounts in China. 

In our tests, none of the politically sensitive e mail messages we sent in English were blocked 

consistently.  One of our e mail accounts, with service provider 21cn.com, did not receive our first 

message containing information about the relatives of protesters injured at the Tiananmen Square 

protest, but 21cn.com did receive this message when we sent it from our second e mail account.  We 

observed the same pattern for the message about surveillance in China we sent to two accounts with 

providers 163.com and 21cn.com. Finally, messages sent in English about media censorship and religious 

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 See Appendix 4 for complete results of our e mail testing. 

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 See Appendix 3 for brief descriptions of the contents of each of the ten e mail messages. 

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